1. Field of the Invention
The present invention relates to a cassette for radiographic imaging and a cassette loading orientation detection device. The cassette for radiographic imaging stores a radiation detector which detects radiation from a subject.
2. Description of the Related Art
An X-ray imaging system which applies radiation such as X-rays to an examinee as a subject and captures X-ray images is known. The X-ray imaging system has an X-ray detector for detecting X-rays that have passed through the examinee. With use of imaging plate (IP) and flat panel detector (FPD) as the X-ray detector, digital processing of X-ray images have been promoted (see, for example, U.S. Pat. No. 7,633,077 (corresponding to Japanese Patent Laid-Open Publication No. 2008-246102) and Japanese Patent Laid-Open Publication No. 2005-204857.
The IP is stored in a container called cassette, and is taken out from an imaging platform every time an image is captured so as to read out the X-ray image recorded on the IP. The FPD, like the IP, is stored in the cassette. Since the FPD converts the incident X-ray into an electric signal to output, there is no need to take out the FPD every time an image is captured, like the IP. However, since the FPD is very expensive, it is often used in more than one imaging platform (for example, platforms for upright-posture imaging and supine-posture imaging). In this case, the FPD is loaded in the imaging platform before capturing an image.
When the cassette is loaded in wrong orientation, the obtained X-ray image is inverted upside down or rotated vertically or horizontally, and thus the X-ray image cannot be obtained in proper direction. In view of this, a radiation image capturing apparatus of U.S. Pat. No. 7,633,077 judges a loading orientation of a cassette (orientation relative to an imaging platform) according to an orientation of the cassette (absolute orientation) and a posture or attitude of an examinee. Based on the judgment result, an X-ray image in a proper direction can be obtained.
Since the X-ray imaging system is very expensive, the conventional system cannot easily be replaced by the system disclosed in the U.S. Pat. No. 7,633,077. Therefore, it may be considered to apply the invention of the U.S. Pat. No. 7,633,077 to the conventional X-ray imaging system. In this case, however, a sensor for detecting the orientation of the cassette needs to be attached to or incorporated in the cassette, and also the posture of the examinee needs to be input every time an image is captured, which is troublesome. Note that the techniques disclosed in the JP-A 2005-204857 does not aim to detect the orientation of the cassette.